1. Field of the Invention
The present invention relates to an image pickup apparatus whose mode can transition among a plurality of modes with different light emission amounts of an illumination light, and an operation method of the image pickup apparatus.
2. Description of the Related Art
Conventionally, an image pickup apparatus such as an endoscope is known, which has a plurality of observation modes with different light amounts of an illumination light to be emitted to an object, and which observes an object while switching these observation modes.
The plurality of observation modes with different light amounts of an illumination light in the endoscope can specifically include a white light observation (white light imaging: WLI) mode in which a white light is emitted to an object, a narrow band observation (narrow band imaging: NBI) mode in which a narrow band light is emitted. Here, while, in the white light observation mode, almost all the light amount which can be emitted by a light source can be employed as an illumination light, in the narrow band observation mode, because only part of the light amount which can be emitted by a light source can be employed, the light amount of an illumination light which can be emitted in the narrow band light observation mode is relatively smaller than the light amount of the illumination light which can be emitted in the white light observation mode. These observation modes are modes for performing observation according to purpose by not only having different absolute light emission amounts, but also making wavelength bands of the illumination light different.
Specifically, in such an image pickup apparatus, a wavelength changing unit such as a filter is provided at a light source apparatus, so that illumination lights with different light amounts and different wavelength bands are radiated.
For example, Japanese Patent Application Laid-Open Publication No. 2009-148487 discloses a technique of, in a light source apparatus in which a plurality of filters for changing a wavelength of a light emitted from a xenon lamp can be disposed on an optical path of the emission light, and an endoscope apparatus, improving response at switching of an observation mode by stopping control of a light amount during operation for changing the wavelength.
According to such a technique, it is possible to reduce brightness disorder of an image during switching of the observation mode. By the way, when the observation mode is switched among a plurality of observation modes, it is necessary to switch setting of an image processing parameter for processing the obtained image, in addition to simply inserting or removing a filter on an optical path of the illumination light. When the image processing parameter is switched, color tone of the image changes.